1. Field of the Invention
The present invention relates to the video monitoring of a viewing field in general. More particularly, the present invention relates to providing a video event trigger when motion is detected and further to tracking motion.
2. Description of Related Art
Video camera technology is the primary mode of monitoring and data acquisition in countless industrial and scientific settings. In many applications, there is a need to know almost immediately when a change occurs within the viewing field so that prompt action can be taken. For example, there may be a need to know when someone is about to enter a hazardous area or when a fire has occurred so that immediate action can be taken. In many of these settings, human observation is simply not adequate because there are extended periods of redundant images not of interest which are only rarely interrupted by an event of interest. Human observation, in such a case, would not only be prohibitively expensive, but could also result in a late or missed triggering. This is especially true considering the boredom associated with such monitoring.
Therefore, there is a need for low cost equipment which can promptly provide an immediate trigger signal. Such equipment is also useful in triggering the start of video recording equipment in a monitoring situation where it is impossible to continuously record the video field.
Even with the current video camera technology, a huge amount of data is produced for every video frame. The video images are presented as long sequences of analog signal voltages per the EIA RS-170 or other standard. Each sequence represents one scan of pixels in a raster line across the video scene, and a multitude of sequences represents one video image, or frame. Pixels are laid out in a video screen in columns and rows (raster lines) with, for example, 480 rows and 512 columns. As a "frame grabber" acquires a sequence of raster lines which represent a video frame, the signal is digitized in an analog-to-digital converter. With a monochromatic ("black and white") system, each digitized pixel is really one byte (8 bits) of information. Therefore, in one frame of a 480 by 512 screen, there almost 2 million bits. As pixels get smaller, i.e., more rows and columns, with newer camera technology, the data per frame increases by a corresponding amount.
There is a need for the capability to produce a video event trigger which can keep up with the video frames as fast as they are produced. The standard frame rate in the United States is 30 frames per second, but new video technology is advancing towards a capability of 1000 frames per second. Even at 30 frames per second, almost 60 million bits of information are created every second for a 480 by 512 frame. Acquiring the ability to correctly and quickly analyze this information poses quite a problem.
In the past, computers have been used to provide video event triggers based on a software algorithm. However, even the fastest computing devices require many tens of milliseconds, to seconds, to analyze the millions of bytes in order to determine whether something interesting has occurred. To achieve faster speeds a very expensive machine is necessary. However, even the best computers are not fast enough. Furthermore, for many applications the volume of the computer (cabinet, memory, etc.) consumes too much space. However, the technology to build the algorithms into silicon gate structures, which require less space and are faster, is too expensive for the small business budget.
Recently, it has been proposed to use a low cost commercially available "fuzzy comparator" chip such as that marketed by Chip Supply Corporation of Florida, formerly Chip Design Corporation, for supplying a video event trigger. According to the manufacturer, this chip utilizes fuzzy logic and neural network technology to evaluate a 20 MHz videotape data stream. However, with only one of these, the hardware approach cannot keep up with the huge onslaught of data.
In the field of camera steadying, a process has been developed to split the viewing field to enable a computer software process to steady the video image. Such a process is used, for example, to remove the inherent vibrations present when video taping from a moving vehicle. However, this method is not directed to providing a video event trigger, and is not concerned with speeding up the process.